QUOTE(davidke20 @ Feb 9 2015, 05:48 AM)
Transmission fluid for gebox. Thick and lasak
Engine oil for engine. Thin and strong detergent to prevent acidic due to hot working environment
Both can't be exchange use. Gebox oil will jam the engine due to too heavy; engine oil can't cope with transmission kinda heavy friction working environment.
to add in, while the specification of SAE for transmission fluid and engine oil is different, the actual viscosity can be the same.
so to say transmission/gear oil is thicker than engine oil is incorrect.
example:
SAE Viscosity Grade (Motor Oil) 5W30
SAE Viscosity Grade (Gear Oil) 75W80
http://www.redlineoil.com/product.aspx?product=50204QUOTE
Vis @ 100°C, cSt 10.4
Vis @ 40°C, cSt 54.1
http://www.redlineoil.com/product.aspx?pid=142&pcid=21QUOTE
Vis @ 100°C, cSt 11.6
Vis @ 40°C, cSt 69
with this, the engine oil is actually thicker than the gear oil!

additionally, detergent is not so much to prevent acidity of the lubricant, more so to be able to clean/neutralize carbon/combustion blow by and keep it in suspension within the oil

there are of course other additives (working along side with detergent) to prevent the oxidization/varnish/acidity of the oil.
As a matter of fact, depending on your driving conditions, transmission can actually be much hotter than your engine oil (remember what i have experienced in my gear oil?) as your engine oil has radiator/coolant to help maintain temperatures, while the gear oil's only way to cool itself is the transmission case which is thick galvanised steel or something (IINM anyways) and those aren't exactly the best materials for heat conductivity

the main reason gear oil cannot be use in an engine is due to the lack of detergent/dispersant additives, while for engine generally it is as you said, as that is made way for detergent/dispersant additives in favor over friction modifiers.

interesting as to how i am answering similar things on both threads
https://forum.lowyat.net/index.php?showtopi...post&p=72920484can consider looking up reports explanation such as this:
http://www.blackstone-labs.com/report-explanation.php
delsooplease consider reading the first page of this thread as well as this thread:
https://forum.lowyat.net/topic/3310512a lot of your questions have been widely available around these forums on various threads (or even google)